The present invention relates to a new and improved method and apparatus for use with a machine tool having hydraulic pallet assemblies which transport workpieces between work stations.
A known machine tool has hydraulic pallet assemblies which are used to move workpieces along a track between work stations. Each of the hydraulic pallet assemblies includes a clamp assembly. The clamp assembly securely holds a workpiece while machining operations are performed on the workpiece at a work station.
During operation of the machine tool, static hydraulic charges are placed on the clamp assemblies to securely grip the workpieces. The static hydraulic charges are maintained throughout movement of the hydraulic pallet assemblies between work stations. There are no hydraulic lines which move along with the hydraulic pallet assemblies. However, the static hydraulic pressures urging the clamp assemblies to their engaged conditions are checked and, if necessary, recharged at the work stations.
Due to their complexity and the conditions under which they are used, the hydraulic pallet assemblies periodically malfunction. Each time a hydraulic pallet assembly malfunctions, the pallet assembly has to be tested and the test results analyzed to determine the cause of the malfunction. The hydraulic pallet assembly is then repaired. The time required to test and repair a hydraulic pallet assembly interrupts normal operations of the machine tool.
When a hydraulic pallet assembly malfunctions, there are several different ways of proceeding. Perhaps the easiest way of proceeding is to do nothing and allow the defective hydraulic pallet assembly to circulate in the machine tool. This results in reduced output until the defective hydraulic pallet assembly is either replaced or repaired. If an attempt is made to repair a defective hydraulic pallet assembly while it is in the machine tool, the operation of the machine tool is interrupted while the repair is made. If it is decided to replace the defective hydraulic pallet assembly with a new pallet assembly, heavy equipment must be used to move the defective hydraulic pallet assembly while the machine tool is idle.